No, you can NOT tell the condition of a tube visually. Well, I guess if the bottle is dark then you know it's not working! Anyway, not a bad rule of thumb, a few years on power tubes depending on how many hours are on the amp and how hard you push the amp. The preamp tubes tend to last much longer than power tubes. Most importantly these days is that preamp tubes tend to be microphonic (noisy) so it can be a pain to find decent tubes... Do have a tech replace the tubes to check for bias and other issues. Great idea to have a tech check out a tube amp even for safety reasons every once in a while... Hope this helps..

Okay some don't like Eurotubes but they are, IMO, solid tubes. I've worked with those guys in the past and they care about their customers. I had an amp changing tone after heating up and Bob walked me through tons of ways to work around the issue even though he said it's mostly likely that it caused by the amp's design and not tubes.

strumminsix wrote:I change mine when they sound bad or I have my tech guy test them. I don't personally buy into changing tubes like changing your oil like some people do.

Agreed, if it sounds good to me, I don't change a thing.

strumminsix wrote:From what I can gather:poweramp 2 years with moderate usage

Probably so, also depends on how hot they are biased.

strumminsix wrote:preamp 4-5 years with moderate usage

On that I do not agree, unless perhaps we are talking about some pretty low quality 12a#7's! I am a preamp tube tinkerer- I like to try out all kinds of different tubes in the different sockets... and try those out in combination with different guitars and speakers! I have slowly amassed a small hoard of old 70's or early 80's RCA, GE, Sylvania and Philips preamp tubes, "JAN" or military spec if possible, NOS if cheap, sometimes out of salvage grab bins... some might not be much good but some turn out to be GEMS. The tubes of this era were built to last at LEAST 30 years (possibly up to double that imho). It can be kind of tedious "work" to keep switching out tubes and playtesting in a (pre)amp to find the right combination, but when you starting getting close, it becomes hard to give up the quest!

Hey Guys,
I might have missed it, but you all know that only the output tubes need to be biased right? Any of the other tubes can be replaced simply by pulling them out and plugging in the new ones. On the issue of microphonic tubes, tap them with a pencil while the amp in on and running. Microphonics will show up quickly. Tip for making tubes last a little longer include, never start playing until the tubes have warmed up for a couple of minutes ( use your standby switch if you have one), and try not to shake the amp too much until the tubes have a chance to cool down for a couple of minutes after shutting the amp off. They're like light bulbs. If you think a tube isn't glowing feel it (carefully) if its hot its glowing whether you can see it or not.

if a tube sounds microponic you will hear it in your playing. Or if you are really suspicious switch your tubes out with fresh ones one at a time to see if it improves.

Not all amps need to be baised - i have three all tube amps and only one of them requires biasing.

If the amp still sounds good - there is only one reason to change tubes - and that is to try out different sounds. You will know a tube is bad when either it is microponic (which you will hear) or it red plates (plates on the tubes glow red - this is very dangerous and tubes need to be changed immediatly when it happens.) You will hear it red plate as well.

If an amp is biased properly and not played too hard the tubes might last forever - depending on thier quality. I have seen some 5E3's straight from the fender tweed era that have been gigged with for 30+ years with thier complete original tube set. The mantra - if it ain't broke - don't fix it comes to mind.

If you want to change your tubes to try and tweak your sound - have fun! but learn how to bias your amp (if it requires biasing) and prepare to go on a seeminly never ending quest for very small differences in tone. (trust me it is quite addictive....each one sounds just a little different - and you can't resist trying to improve.)

Oh - and just FYI if you do get new power tubes my favorite new production tubes are the TAD 6L6GC-STR

Hey Rev, How do you hear that a tube is microphonic or red plated? Can you decribe the sound. I've had my Heritage Patriot for just over 2 years and have about 100 shows played on these tubes. It still sounds great, but that amp is in my main rig and I would rather be proactive on the retubing than to have a blowout in an upcoming show. Right now, my tubes glow a beautiful blueish purple with a slight rose color at the plate. I am told they are in tip top shape right now.